1. Field of the Invention
The present invention relates to a liquid crystal display (LCD), and in particular relates to a driving circuit driving a liquid crystal pixel array of the LCD.
2. Description of the Related Art
A liquid crystal display (LCD) is a thin, flat electronic visual display that uses the light modulating properties of liquid crystals. Liquid crystals do not emit light directly. An image is displayed by controlling the transmission of the liquid crystals.
For each liquid crystal pixel, it is only the magnitude of the applied voltage that determines the light transmission. To prevent polarization (and rapid permanent damage) of the liquid crystal material, the polarity of the applied voltage is reversed on alternate video frames. Several polarity inversion techniques have been developed, which include line inversion, dot inversion and column inversion.
For polarity inversion, a common voltage is required. When the applied voltage is greater than the common voltage, a positive polarity display is provided. On the contrary, when the applied voltage is lower than the common voltage, a negative polarity display is provided. For the dot inversion (as shown in FIG. 1A) or column inversion (as shown in FIG. 1B) techniques, the polarity of each pixel is reversed in each frame, and two adjacent pixels (such as a first pixel P1 and a second pixel P2) located in the same row and adjacent columns are always of opposite polarities. Because the pixels, such as the first and second pixels P1 and P2, in the same row may share the same common voltage, the common voltage has to be fixed to a constant value and is known as a DC VCOM. However, a constant DC VCOM may cause redundant power consumption in the driving circuit; which is discussed and reduced in the embodiments of the invention.